1. Field of the Invention
The present invention relates to a reflection type liquid crystal display apparatus and a liquid crystal projector system.
2. Description of the Related Art
Nowadays, an age of multimedia has begun, and equipment communicating by using image information has been more and more important. Among others, since being thin and having small power consumption, a liquid display apparatus have been paid attention, and have grown up to a key industry comparable to the semiconductor industry.
As for the liquid crystal display apparatus, today, as the screen size becomes larger, not only the price of a manufacturing apparatus becomes higher but also rigorous  electrical properties are required for driving the large screen. Therefore, a projection type liquid crystal display apparatus where a small size liquid crystal display panel is prepared, and an image is optically enlarged and displayed, has been paid attention. This is because, similar to a scaling law where, as the size of a semiconductor becomes smaller, the performance and the price of the semiconductor, become better, it is possible not only to improve the properties of the liquid crystal display apparatus by causing the size to be smaller, but also to reduce the cost of the liquid crystal display apparatus. However, since an image is enlarged by irradiating a light on a small size liquid crystal display panel, the influence of the light to a semiconductor circuit can not be ignored. Therefore, for example, in U.S. Pat. No. 5,706,067, a liquid crystal display apparatus is disclosed, where, by using a light shielding layer such as a lamination film of Ti and TiN, light incidence into a semiconductor circuit is protected.
However, in the projection type liquid crystal  display apparatus, brighter displaying is required, thereby the liquid crystal display apparatus is irradiated with a more intense light. Therefore, it is difficult to entirely protect a light from entering in the semiconductor circuit by merely using the light shielding layer, rather a part of the light enters the semiconductor circuit, thereby photo carriers may be generated in the semiconductor circuit. Once the generated photo carriers reach to a switching element of the semiconductor circuit, there is a possibility that an adverse affect is given to the operation of the switch element, thereby, normal displaying operation cannot be performed. Such an adverse affect with respect to the switch element due to the photo carriers, is referred to as light leakage.
Therefore, in Japanese Patent Application Laid-Open No. H08-146458, it is disclosed to provide an n-type semiconductor region which is the same type as the type of a drain region of a switching element provided to a p-type Si substrate, and has an area larger than the area of the drain region, to the surroundings of the drain region.  Furthermore, by fixing the potential of the p-type Si substrate to the ground potential using a ground electrode, a positive bias is applied to the n-type semiconductor region. By this procedure, positive holes and electrons of the photo carriers generated in the p-type Si substrate are absorbed in the ground electrode and the n-type semiconductor region, respectively. Therefore, it is possible to reduce the adverse affect due to the photo carriers generated by the light reached to the p-type Si substrate, with respect to the operation of the switching element.